We study mixtures of decomposable graphical models, focusing on their ideals and
dimensions. For mixtures of clique stars, we characterize the ideals in terms of ideals
of mixtures of independence models. We also give a recursive formula for their ML
degrees. Finally, we prove that second secant varieties of all other decomposable
graphical models have the expected dimension.
Keywords
graphical models, secant varieties, decomposable graphs,
dimension, identifiability, clique sums, maximum likelihood
estimation, expected dimension, ideals of secant varieties